The major objective of this proposal is to evaluate a multivalent fusion protein vaccine against lymphatic filariasis in a rhesus macaque model. Preliminary studies in macaque using a recombinant WbHAT vaccine plus alum showed that approximately 40% protection can be achieved against a challenge infection. Although this is significant, compared to our published findings using the same vaccine in rodent model, the values were substantially low. Vaccination trials using rBmHAT plus alum or rBmHAX plus alum in three rodent models showed that close to sterile immunity (95-97%) can be achieved. Thus, there is a significant difference in the degree of protection conferred following vaccination in th rhesus macaque and rodents. Analysis of the characteristics of the protective responses showed that in rhesus macaques the responses are predominantly Th2 with little or no Th1 response. A similar analysis in rodents and the human showed that balanced Th1/Th2 responses are critical for protection against lymphatic filariasis. This might explain the low protection observed in our rhesus macaque trial. In an effort to increase the Th1 responses towards the vaccine antigen and thus increase the rate of protection, in this application, we are proposing to use AL019 adjuvant, which is a combination of alum plus TLR4 agonist. Preliminary studies in rhesus macaque using AL019 as an adjuvant for rWbALT-2 showed that the adjuvant promotes both Th1 and Th2 responses and the rate of protection was doubled suggesting that AL019 is an excellent adjuvant for lymphatic filariasis vaccine in macaque. Therefore, in this application we are proposing an initial vaccination trial in macaque using rWbHAT and rWbHAX plus AL019 and down select the best formulation based on immunogenicity, safety, and correlates of protection. Selected vaccine candidate will be then further characterized and vaccination regimen will be optimized in a jird and hamster model. Finally the prophylactic and therapeutic potential of the selected vaccine formulation will be evaluated in detail in the macaque model. Several rounds of mass drug administration (MDA) have tremendously reduced the incidence of lymphatic filariasis in the endemic regions. Therefore, there is a need to maintain the momentum gained by MDA and leverage the success towards developing a sustained eradication strategy such as an effective vaccine for lymphatic filariasis. We have proposed three aims in this application. Specific Aim 1 is aimed at evaluating the immunogenicity of rWbHAT and rWbHAX in rhesus macaque and down select the best vaccine formulation for further development. Based upon our findings from rodent vaccination trial, either of the vaccines will be highly efficient as prophylactic vaccines. In Specific Aim 2 e will characterize the prophylactic and therapeutic potential of the down selected vaccines in a jird model. We decided to do these characterization studies in jirds mainly because of cost, time, repeatability, ability to accurately determine the parasite establishment, and the fact that bigger sample size are possible. Preliminary studies in the jirds showed that rWbHA, a major component of the two selected vaccine candidates have significant therapeutic activity. Thus, this aim will focus on characterizing the mechanism of the therapeutic activity and evaluate if combining the vaccine with anti-filarial treatment can achieve total clearance of the infection from infected jirds. Several studies show that hookworm infections coexist with lymphatic filariasis infection in the endemic regions. Therefore, this aim will also evaluate the effects of hookworm infections on the vaccine-induced immunity against lymphatic filariasis. Finally in Specific Aim 3 we will evaluate the prophylactic and therapeutic potential of the down selected and optimized multivalent vaccine formulation in rhesus macaque model. We will also test if combining anti-filarial treatment with the therapeutic vaccination is beneficial. Similarly we will also test the role of hookworm infection in the development of vaccine-induced immunity in macaques. Overall, these studies are aimed at selecting the most effective vaccine formulation for possible testing in the human clinical trials.